Title of Invention

A DEVICE FOR TESTING THE FUNCTION OF SCATTERED-LIGHT SMOKE SENSORS

Abstract

The invention relates to a device for testing the function of scattered-light smoke sensors which comprise a measuring chamber having a measuring light source, which transmits light pulses, and a measuring light receiver with an adapter which contains a test light source, actuatable in synchronism with the light pulses of the measuring light source, for supplying the measuring light receiver with test light pulses, characterized in that the adapter comprises a detector which responds to the electromagnetic field generated by the current pulses of the measuring light source and which controls the test light source.

Full Text

The present invention relates to a device for testing the function of scattered-light smoke sensors, which comprise a measuring chamber having a measuring light source, which transmits light pulses, and a measuring light receiver, with an adapter which contains a test light source, actuatable in synchronism with the light pulses of the measuring light source, for supplying the measuring light receiver with test light pulses. As is known, the measuring chamber of scattered-light smoke , sensors is screened as tightly as possible from light from the exterior in order to render the sensor substantially immune to external light. However, this screening cannot be absolute since the sensors must be open to the outer atmosphere to enable smoke to penetrate into the measuring chamber. To minimise the disturbing influence of the external light, which enters the measuring chamber in spite of the screening, the analysis circuit of the sensor is designed such that the measuring light receiver reacts only to light received within a defined time window following the triggering of the particular light pulse of the measuring light source. In a sensor test device of the type referred to in the introduction, as described in EP-A-0 636 266 (US-A-5,523,744), the test light transmitter is actuated by an additional light receiver which is arranged in the sensor test device and which triggers the test light source upon the reception of a light pulse from the measuring light source. Since, due to the forementioned screening of the measuring chamber from external light, the additional light receiver cannot receive the light pulses in every position of the sensor test device relative to the sensor, but only in specific positions, in this sensor test device positioning means are provided which ensure that in the test state the sensor test cievice is always in the same alignment relative to the sensor. In this alignment, the measuring light source and additional light receiver of the sensor test device, and likewise the test light source and measuring light receiver, assume defined relative positions in which it is ensured that the light pulses of the measuring light source reach the additional light receiver, and the light flashes from the test light source reach the measuring light receiver. As the positioning means require the provision of corresponding guide means on the smoke sensors, this sensor test device can be used only in the case of sensors of a specific type and in principle cannot be used in sensors without such guide means. The invention is now to provide a sensor test device which functions satisfactorily in any position of alignment relative to the sensor to be tested and which thus can be used universally and can easily be adapted to different types of sensors. This object is achieved, in accordance with the invention, in that the adapter comprises a detector which responds to the electromagnetic field generated by the current pulses of the measuring light source and which controls the test light source. Thus in the case of the sensor test device according to the invention, it is not the light pulses as such, transmitted from the measuring light source, which are detected but rather the electromagnetic field generated by the current pulses triggering the light pulses. As this field surrounds the sensor on all sides and relatively homogeneously, the sensor test device can detect the light pulses in any alignment relative to the sensor. A first preferred embodiment of the device according to the invention is characterised in that the forementioned detector is formed by an induction coil. A second preferred embodiment of the device according to the invention is characterised in that the adapter has a prismatic, box-like form and in the manner of a remote control can be directed towards the smoke sensor to be tested, or can be placed onto the dome of a smoke sensor lying on a base. A third preferred embodiment of the device according to the invention is characterised in that the adapter has a rotation-symmetrical can- or pot-shaped form, open at one end, and can be applied to or slipped over the sensor to be tested, and that the induction coil is arranged on the inside of the adapter. Preferably, the induction coil is arranged in the vicinity of the edge on the open side of the adapter or on the bottom opposite the open side. A fourth preferred embodiment of the device according to the invention is characterised in that means are provided for reflecting the test light pulses into the measuring chamber. These means for reflecting the test light pulses, which naturally can also be means for scattering the test light pulses, ensure that with any alignment of the sensor test device relative to the sensor, a sufficient proportion of the test light pulses is guided into the measuring chamber and reaches the measuring light receiver. A fifth preferred embodiment of the device according to the invention is characterised in that the forementioned means for reflecting the test light pulses are formed by a reflective coating arranged on the inside of the adapter. The sensor test device according to the invention can be used in principle to test any type of scattered light sensor so that it is possible to dispense with the relatively costly test gas normally used for sensor testing. This not only results in a reduction in costs but also facilitates substantially faster testing of entire lines of sensors since each sensor is fully operational immediately following the test and does not, as in the case of testing with test gas, comprise a measuring chamber filled with test gas and thus block the further testing due to successive alarms. The two embodiments of the adapter, either in the form of a small box in the manner of a remote control, or in the form of a pot which can be slipped over or applied to the sensor, are provided for different applications. The pot-shaped form is preferably used wherever it is necessary to test sensors mounted on a ceiling, which is carried out from the floor of the room in question. In this case the adapter is installed in a hood-shaped housing which is secured to a tubular connecter extensible by extension tubes. The adapter in the form of a remote control is preferably used in test laboratories in which the sensors to be tested are mounted not on the ceiling but on a panel or test bench, or however for sensors which are mounted within apparatus or air discharge channels and which are not easily accessible to the pot-shaped adapter. Another preferred embodiment of the device according to the invention is characterised by an electronic circuit for synchronising the triggering of the test light pulses with the light pulses from the measuring light source, which circuit comprises a stage for gating interference pulses out of the signal supplied by the induction coil, comprising an amplifier and an electronically controlled voltage divider, the operating point of the amplifier being automatically offset by the controlled voltage divider such that the interference pulses are gated out and the measuring pulses produced by the pulses from the measuring light source are satisfactorily recognized. Accordingly, the present invention provides a device for testing the function of scattered-light smoke sensors, which comprise a measuring chamber having a measuring light source, which transmits light pulses, and a measuring light receiver, with an adapter which contains a test light source, actuatable in synchronism with the light pulses of the measuring light source, for supplying the measuring light receiver with test light pulses, characterized in that the adapter comprises an induction coil which responds to the electromagnetic field generated by the current pulses of the measuring light source and which controls the test light source. In the following the invention will be explained in detail in the form of an exemplary embodiment, making reference to the drawings in which: Figure 1 is a schematic illustration of a sensor test device according to the invention and Figure 2 is a block diagram of the circuit for synchronising the measuring light source and the test light source. The sensor test device illustrated in Figure 1 serves for the function testing of smoke sensors on site, thus generally sensors mounted on the ceiling of a room, and for this purpose is designed such that from below it can be applied to or slipped over the sensors to be tested. The sensor test device is particularly suitable for sensors whose housing has the approximate shape of a spherical calotte or truncated cone. Such sensors are represented for example in International Model Protection Registrations DM/028 534 and DM/034 103. This reference is not to be understood as a limitation to the foresaid types of sensors; naturally, the sensor test device according to the invention can be used, with possible slight adaptations, in virtually all modern scattered-light smoke sensors. As illustrated in the drawing, the sensor test device substantially comprises a rotation-symmetrical, pot-like adapter 1 open at one end, an induction coil 2 arranged on the inside of the adapter 1, a light source 3 arranged at a short distance in front of the edge of the adapter 1 on its open side, and an electronics unit 4 arranged in the region of the bottom of the adapter. As illustrated in the Figure*! the induction coil 2 can be arranged on the bottom of the adapter 1 or also at its upper edge, for example at the level of the light source 3. As indicated in the Figure by a partially represented, scattered-light smoke sensor M, the sensor test device is applied to or optionally slipped over the sensor to be tested. For a more detailed description of the smoke sensor M, reference is made to EP-A-0 636 266, EP-A-0 821 330 and the scattered-light sensors of the AlgoRex series (AlgoRex = registered trade mark of Cerberus AG). The smoke sensor M comprises a measuring chamber 5, screened from external light, having a measuring light source 6 and a measuring light receiver 7 whose optical axes extend at an angle to one another and intersect in the central region of the measuring chamber 5. The measuring light source 6 transmits short, intensive light pulses into the central region of the measuring chamber 5, no light beams being able to travel on a direct path from the measuring light source 6 to the measuring light receiver 7 due to the selected arrangement. Therefore the measuring light receiver 7 "sees" the forementioned central region of the measuring chamber 5, but not the measuring light source 6. The light from the measuring light source 6 is scattered by smoke penetrating into the measuring chamber 5 and a part of this scattered light falls onto the measuring light receiver 7. As the measuring chamber 5 must be designed such that smoke can penetrate therein, the light screening of the measuring chamber also cannot be complete and therefore a component of external light, albeit very small, must be expected inside the measuring chamber 5. To eliminate possible disturbing influences of this residual external light, the analysis electronics of the sensor M are designed such that the measuring light receiver 7 reacts to received scattered light only when this light arrives within a specific time interval following the transmission of a light pulse by the measurihg light source 6. The transmission of a light pulse by the measuring light source 6 thus opens a time window in the analysis electronics, so that processing takes place only of those signals received by the measuring light receiver 7 which have been generated within this time window. In the function testing of the smoke sensor M to be performed using the illustrated sensor test device, intermittent light from the light source 3 of the sensor test device, which in the following will be referred to as the test light source, are superimposed upon the light pulses of the measuring light source 6. These test light pulses enter the measuring chamber 5 of the smoke sensor M and herein pass to the measuring light receiver 7; following the reception of one or more test light pulses, in the sensor M an alarm is then triggered which is recognised by the alarm indicator of the sensor or in the associated signal control centre. This alarm triggering serves as a criterion that the sensor is functional. To ensure that, with any alignment of the sensor test device relative to the smoke sensor M, the largest possible proportion of the test light pulses is directed into the measuring chamber 5 and reaches the measuring light receiver 7, at the level of the test light source 3 a strip-shaped region of the inner wall of the sensor test device can be provided with a reflective coating 8. The induction coil 2 detects the electromagnetic field generated by each light pulse of the measuring light source 6 and controls the test light source 3 in such manner that the test light source 3 transmits test light pulses within the aforementioned time window. For the focusing of the forementioned electromagnetic field onto the induction coil 2, the induction coil 2 is surrounded by an upwardly open, metallic cylinder 9 which can be covered on its upper end side by a foil 10 permeable to electromagnetic energy. However the foil can also be arranged above the cylinder 9. The adapter 1 is installed in a hood-shaped housing 11 which is mounted on a socket 12. A tubular connecter 13, to which an extension tube can be applied, is inserted into said socket 12. Using several of these extension tubes, which are connectible to one another by tube clamps, the sensors can be tested up to a room height of approximately 7 m. The current supply to the sensor test device is provided either via batteries or via a mains cable, the battery compartment or power supply unit being arranged on the lowest extension tube. This box-like device member, which also contains a switch for the switching on and off of the sensor test device, has been referenced BF in Figure 1. The housing 11 can also be connected to the tubular connecter 13 via a fork-shaped adapter (not shown), as is the case in the sensor test devices for the forementioned AlgoRex sensors. Figure 2 is a block circuit diagram of the circuit 4 which is connected to the adapter 1 containing the induction coil 2 and which serves to synchronise the test light source 3 with the measuring light source 6. As shown in the drawing, the circuit 4 contains a first pre-amplifier stage 14 connected to the induction coil 2, a high/low-pass filter 15 connected to the first pre-amplifier stage 14, a second pre-amplifier stage 16 connected to the filter 15, an end stage 17 connected to the second pre-amplifier stage 16, and a stage 18, which cooperates bidirectionally with said end stage 17, for the gating out of interference pulses and for automatic gain control. The end stage 17 is connected to an active time filter 19 which in turn is connected to a difference analysis stage 20. The difference analysis stage 20 is followed by a stage 21 for generating the electric pulse for triggering the test light pulse, and the stage 21 is followed by a voltage transformer 22 arranged upstream of the test light source 3. The voltage transformer 22 is preferably arranged in the device member BF (Figure 1). The test light source 3 is formed by a flash lamp or flash tube, for example a xenon tube, and the voltage transformer 22 serves to make available the voltage required for igniting the flash lamp. A connection 23 for the suppression of flash interference extends between the voltage transformer 22 and the end stage 17. The measuring light source 6 (Figure 1), which is formed for example by an infrared diode (IRED), transmits a light pulse at regular intervals of for example 1 to 3 seconds, whereby a voltage pulse MP with a duration of approximately 100 \is, referred to in the following as measurement pulse, is induced in the induction coil 2. This measurement pulse is very small and amounts to a few millivolts. In the induction coil 2, voltage pulses are induced of course not only by the pulses of the measuring light source but also by the various communications currents on the sensor lines. The measurement pulses MP differ from these interference pulses designated SP substantially by virtue of their distinctly lower frequency and their duration. The voltage pulses induced in the induction coil 2 are amplified in the first pre-amplifier stage 14 and the coarsest interference pulses are then filtered out in the high/low-pass filter 15. After further amplification in the second pre-amplifier stage 16, the signal passes to the end stage 17 and to the stage 18 for the gating-out of interference pulses and automatic gain control. In this stage, which substantially contains an amplifier, an electronically controlled voltage divider and a storage capacitor, by offsetting of the operating point of the amplifier by means of the adjustable resistance, the measurement pulses MP and the interference pulses SP are offset on different sides relative to the zero line, and as shown in the drawing, the measurement pulses MP are offset into the negative sector and the interference pulses SP into the positive sector. Consequently the interference pulses can be easily gated out. Automatic gain control is effected by means of the voltage divider. Following the gating out of the interference pulses SP in the stage 18, a measurement pulse MP, which has been very largely freed of interference pulses and is formed by a characteristic double pulse, is available in the end stage 17, said measurement pulses MP having a steep rising edge which is subsequently used to trigger the flash (test light pulse) of the test light source 3. As it cannot be ruled out that the output signal of the end stage 18 is still adulterated by interference pulses, further smoothing and damping of any disturbances which may still be present take place in the active time window 19, whereby the measurement pulse MP acquires the illustrated sawtooth formation. The flash is triggered when the measurement pulse MP overshoots a specified threshold value. To prevent the flash from being triggered by an interference pulse which is still present, the threshold value must not be too small; on the other hand it also must not be too great in order that it can also be triggered by smaller measurement pulses corresponding to weaker light pulses of the measuring light source. As shown in the drawing, the forementioned threshold value designated SW is positioned in the centre of the rising edge in the difference analysis stage 20. Upon the overshooting of the threshold value SW by the rising edge of the measurement pulse MP, a pulse for the triggering of the test light source (flash lamp) 3 is generated in the stage 21. This pulse has the illustrated rectangular form and preferably has a somewhat longer duration than the measurement pulse MP, for example approximately 200 ys. The flash interference suppression, which suppresses the disturbing influence of the flash of the test light source 3 upon the gain control, as the latter does not function in the desired manner for a short time period following the triggering of the flash, consists in that the control means contained in the stage 18 is blocked for the duration of the flash. As an alternative to the form illustrated in Figure 1, the adapter can also have the form of an elongate prism in the manner of a remote control for electronic apparatus or for door openers for garage doors. Such an adapter is preferably used to test smoke sensors in laboratories or in apparatus or air discharge channels with poor accessibility. For the testing of sensors, this adapter is either directed towards the sensors at a short distance therefrom or the adapter is placed on the dome of the sensors when these are arranged on a horizontal panel or a horizontal desk with the dome facing upwards. Practical experiments have shown that with the adapter in this position, even in the case of sensors having a flat "dome", the test light pulses transmitted from the test light source reach the measuring light receiver, which obviously occurs due to the scattering of the test light pulses on particles contained in the air in the room. A.t its end which, during the testing, faces towards the sensor to be tested, the adapter contains an outlet window for the passage of the test light pulses and an infrared filter for said test light pulses, so that the light flashes are no longer experienced as disturbing. WE CLAIM: 1. A device for testing the function of scattered-light smoke sensors (M), which comprise a measuring chamber (5) having a measuring light source (6) which transmits light pulses, and a measuring light receiver (7), with an adapter (1) which contains a test light source (3), actuatable in synchronism with the light pulses of the measuring light source, for supplying the measuring light receiver (7) with test light pulses, characterized in that the adapter (1) comprises an induction coil (2) which responds to the electromagnetic field generated by the current pulses of the measuring light source (6) and which controls the test light source (3). 2. The device as claimed in claim 1, wherein the said detector is an induction coil (2). 3. The device as claimed in claim 1 or 2, wherein the adapter has a prismatic, box-like form and in the manner of a remote control can be directed towards the smoke sensor (M) to be tested, or can be placed onto the dome of a smoke sensor lying on a base. 4. The device as claimed in claim 3, wherein at its end which, during the testing, faces towards the sensor (M) to be tested, the adapter contains a window for the passage of the test light pulses and an infrared filter for said test light pulses. 5. The device as claimed in claim 1, wherein the adapter (1) has a rotation-symmetiical, can- or pot-shaped form, open at one end, and can be applied to or slipped over the sensor (M) to be tested, and that the induction coil (2) is arranged on the inside of the adapter (1). 6. The device as claimed in claim 5, wherein the induction coil (2) is arranged in the vicinity of the edge on the open side of the adapter (1) or on the bottom opposite the open side. 7. The device as claimed in claim 5, wherein means (8) are provided for reflecting the test light pulses into the measuring chamber (5) and that these means are formed by a reflective coating (8) arranged on the inside of the adapter (1). 8. The device as claimed in claim 7, wherein the test light source (3) is arranged in the vicinity of the edge on the open side of the adapter (1), and the reflective coating (8) is formed by a strip-shaped region adjacent to said edge. 9. The device as claimed in claim 6, wherein the bottom part of the adapter (1) containing the induction coil (2) is covered by a foil (10). 10. The device as claimed in claim 1, wherein the test light source (3) is a flash lamp. 11. The device as claimed in any one of claims 3 to 10, wherein an electronic circuit (4) is provided for synchronizing the triggering of the test light pulses with the light pulses of the measuring light source (6) which circuit (4) comprises a stage (18), for gating interference pulses (SP) out of signal supplied by the induction coil (2), which contains an amplifier and an electronically controlled voltage divider, the operating point of the amplifier being automatically offset by the controlled voltage divider such that the interference pulses (SP) are gated out and the measurement pulses (MP) produced by the pulses of the light source (6) are satisfactorily recognized. 12. The device as claimed in claim 11 wherein the duration of each test light pulses, the controller of the stage (18) for gating out interference pulses is blocked. 13. A device for testing the function of scattered-light smoke sensors, substantially as herein described with reference to the accompanying drawings.

Documents:

0619-mas-1999 abstract-duplicate.pdf

0619-mas-1999 abstract.jpg

0619-mas-1999 abstract.pdf

0619-mas-1999 claims-duplicate.pdf

0619-mas-1999 claims.pdf

0619-mas-1999 correspondnece-others.pdf

0619-mas-1999 correspondnece-po.pdf

0619-mas-1999 drawings-duplicate.pdf

0619-mas-1999 drawings.pdf

0619-mas-1999 form-1.pdf

0619-mas-1999 form-13.pdf

0619-mas-1999 form-19.pdf

0619-mas-1999 form-26.pdf

0619-mas-1999 form-3.pdf

0619-mas-1999 form-4.pdf

0619-mas-1999 form-5.pdf

0619-mas-1999 petition.pdf